1. Field of the Invention
The present invention relates to an optical pickup device used in an optical storage device for recording (writing) and/or reproducing (reading) an information signal by using an optical recording medium such as an optical disk, a magneto optical disk or the like and a biaxial actuator for the optical pickup device and, more particularly, to the structure of a bobbin having an objective lens opposing an information recording surface of an optical recording medium, a holder therefor, a member obtained by coupling the objective lens and the hold, and a coil member.
2. Description of the Related Art
In an optical disk storage device for recording and/or reproducing an information signal by using an optical disk such as a read-only optical disk, a phase change optical disk or a magneto optical disk on which an information signal can be recorded and reproduced or the like as an optical recording medium, an optical disk is placed on a disk table attached to the rotating shaft of a spindle motor to be rotatably driven, and an optical head of an optical pickup device can approach or leave from the spindle motor.
An optical pickup device has a light source for emitting a laser beam, a photo detector for receiving a laser beam obtained by reflecting the laser beam emitted from the light source by an information recording surface of an optical disk, and the like. An objective lens of the optical head is arranged to oppose the information recording surface of the optical disk. A laser beam converged by the objective lens and irradiated in a direction almost vertical to the information recording surface is reflected by the information recording surface, transmitted through the objective lens again, and received by the photo detector. When the objective lens is moved from the inside to the outside in the radial direction along the information recording surface of the optical disk, so that an information signal can be recorded on the information recording surface, or an information signal recorded on the information recording surface can be reproduced.
As a biaxial actuator of such an optical pickup device, for example, a biaxial actuator as shown in FIG. 1 and FIG. 2 is known. This biaxial actuator 1 includes a movable portion 3 having an objective lens 2 to be opposed to an information recording surface of an optical disk, a fixed portion 5 for elastically supporting the movable portion 3 through a support member 4, and a base member 6 to which the fixed portion 5 is fixed, and the like.
The movable portion 3 has a holder 7 which holds the objective lens 2 such that the objective lens 2 is adhered to the holder by an adhesive agent and a square-cylindrical bobbin 8 coupled to and integrated with the holder 7, and a focus drive coil 9 is wound on the bobbin 8 in a direction perpendicular to the optical axis direction of the objective lens 2. A pair of tracking drive coils 10, 10 are attached to the outside of the focus drive coil 9 on one side of the bobbin 8 such that the tracking drive coils are wound in a direction parallel to the optical axis direction of the objective lens 2.
One ends of two suspension wires 4 serving the support members are vertically attached to each of both of the side portions of the holder 7 of the movable portion 3 with a predetermined gap in an up and down direction. The other ends of the suspension wires 4 extend on the opposite side of the objective lens 2 and fixed to the wire support block 5 serving as a fixed portion. The wire support block 5 is fixed to the actuator base 6 serving as a base member by a fixing means serving as a fixing screw 11. The winding end portions of the focus drive coil 9 and the tracking drive coils 10 are wound on the suspension wires 4 on the movable portion side, and soldered to be conductive lines for supplying a current to the focus drive coil 9 and the tracking drive coils 10.
A pair of yokes 12 are planted in parallel on the actuator base 6 with a predetermined gap in a direction in which the suspension wire 4 extends. Magnets 13 are respectively fixed to the opposite surfaces of both the yokes 12 by a fixing means using an adhesive agent. In the gap where the pair of magnets 13 are opposite to each other, one side of the bobbin 8 to which the tracking drive coils 10 is attached is inserted with a predetermined gap.
In this manner, when a current is supplied to the focus drive coil 9 through the suspension wires 4, a thrust in an optical axis direction (focus direction) is generated by the magnetic flux generated by the magnets 13, so that the objective lens 2 moves in the optical axis direction thereof to perform focusing control. In addition, when a current is supplied to the tracking drive coils 10 through the suspension wires 4, a thrust in a direction (i.e., a tracking direction) perpendicular to the optical axis is generated by the magnetic flux generated by the magnets 13, so that the objective lens 2 moves in the perpendicular direction thereto to perform tracking control.
On the basis of the focusing control of the focus drive coil 9 and the tracking control of the tracking drive coils 10, a focal point of a laser beam converged by the objective lens 2 flows up a periodic move of a recording track on the information recording surface of the optical disk, and the focal point is always formed on the recording track.
However, in the biaxial actuator of the conventional optical pickup device described above, the objective lens 2 and the holder 7 are constituted by independent members, respectively, and the objective lens 2 and the holder 7 are adhered to each other by an adhesive agent to be integrated with each other. For this reason, the following problem is posed.
More specifically, when the adhesive agent is used as the means for fixing the objective lens 2 and the holder 7 to each other, the adhesive agent is distorted by contraction caused by hardening of the adhesive agent in assembly, contraction caused by hardening based on a change in temperature, degradation, or the like after the adhesion, extension caused by softening, or the like, the assembly precision of the objective lens 2 may vary, or an attaching position or an attaching state thereof may change. In addition, when the adhesive agent is used, not only the number of assembly steps increases, but also the adhesive agent is uneconomical because the cost of the adhesive agent itself increases.
The present invention has been made in view of the above problem, and has as its object to solve the above problem by forming an objective lens and a holder such that the objective lens and the holder are integrally molded by a synthetic resin which can transmit a laser beam.
According to the present invention, in order to solve the above problem or the like and achieve the above object, there is provided a biaxial actuator which comprises an objective lens for converging a laser beam emitted from a light source to be irradiated on an information recording surface of an optical recording medium and guiding a laser beam reflected by the information recording surface to a photo detector, and a holder for causing the objective lens to oppose the information recording surface with a predetermined gap, which is characterized in that the objective lens and the holder are formed to be integrally molded by using a synthetic resin which can transmit the laser beam.